Signal device



W. W HAY SIGNAL DEVICE June 30, 1959 Filed Dec. 23, 1957 FIG. 2

IN VEN TOR. WAY N E W. H AY g wzm WW ATTORNEY & GENT SIGNAL DEVICE Wayne W. Hay, Madison, Wis., assignor to. Air Reduction Company, Incorporated, New York, N.Y., a corporation of New York Application December 23, 1957, Serial No. 704,808

5 Claims. (Cl. 116-70) The invention relates to a signal device and particularly to such a device for use in inhalant anesthetic administering apparatus adapted to afiord a warning signal in the event of an interruption or failure of a gas being administered to a patient.

The need for such an alarm will be readily understood when the conventional type of anesthetic administering apparatus is considered. Such apparatus frequently are referred to as anesthetic gas machines. The gaseous mixture comprising a mixture of air or oxygen and one or more anesthetic gases or vapors, is breathed by the patient through any suitable inhaler such as a face mask. Various types of systems or circuits may be associated with the inhaler in which the patients exhalation may either be recycled in a closed network, only partially rebreathed, or discharged with no rebreathing. In systems characterized by rebreathing, the exhalations are passed through an absorber for removal of carbon dioxide. The anesthetic machine embodies various conduits, control valves and flow meters for regulating the delivery of the constituent gases and permitting the control of the administration by the anesthetist. The respective gases, commonly, are supplied in individual cylinders in which they are compressed and thence discharged at reduced pressure as required. For example, oxygen and the anesthetic gases such as cyclopropane and nitrous oxide are supplied in this way, in small cylinders carried in the anesthetic machine. Volatile anesthetics such as ethyl ether are vaporized and administered as vapor in admixture with other gases.

It is readily apparent that the continued availability of the various gases administered to the patient is extremely important. The usual pressure gages and flow meters provide indications from which the operator may determine the supply. However, in the presently available apparatus, there is no arrangement for automatically signalling the depletion of one or more of the gases and it is the responsibility of the anesthetist or the operator to avoid the failure or interruption of any of the gases which are being administered. This must be done by frequent periodic checking of the gas controls. As a practical matter, however, it is possible, when the anesthetists attention is required elsewhere in the performance of his duties or even momentarily diverted, for one of the gases to become depleted without the operator immediately becoming aware that this has occurred.

This eventuality can be hazardous under certain circumstances, even when its occurrence is undetected for only a relatively short time. For example, where a considerable amount of nitrous oxide is employed as a diluent in admixture with the required amount of oxygen and with normal anesthetic concentrations of volatilized ethyl ether vapors, according to a common technique, interruption or failure of the nitrous oxide quickly results in the formation of extremely high and possibly injurious concentrations of the ether vapors in the delivery mixture. The consequent hazard could readily be corrected nited States Patent or avoided if the failure of the nitrous oxide were immediately called to the attention of the anesthetist, permitting him to readjust the setting of the ether vaporizer or other gas supply valves and thus diminish the relative concentration of the ether vapors. In any event, it can readily be appreciated that such circumstances require the immediate notification of the anesthetist that such depletion of the gas supply has either taken place or is substantially about to occur. It would, of course, be preferable to produce a suitable alarm or signal which would occur prior to complete exhaustion of any one of the gases, so that a suitable period would be allowed for furnishing a fresh supply of the gas and thus completely avoid any interruption therein.

Although other devices employed in certain gas installations or systems might suggest themselves, none has been found that is completely suitable for use in connection with anesthetic administering apparatus. Thus, for example, electrically energized signal devices available for other purposes may not be employed for the purposes above described because of the hazards presented by the presence of ignitible anesthetic gases. Similarly various mechanical means, possibly suitable for other purposes, are not sufiiciently simple or compact in construction, and frequently include mechanisms or elements whose need of frequent replacement or adjustment render them insufiiciently reliable, or too cumbersome, for use in apparatus of this type.

Accordingly, it is an object of the present invention to provide an alarm device for inhalant anesthetic administering apparatus, which is of simple and reliable con- It is a further object of the invention to provide such an alarm device which operates mechanically in response to a drop in pressure, upon the depletion of a specified gas source, below a predetermined safe value and which automatically resets upon the substitution or provision of an adequate source.

A further object of the invention is to provide such a mechanical signal device in which the number of movable and operable members thereof is minimized and which is of the utmost durability and reliability of operation.

According to one embodiment of the invention, the above objects are accomplished by providing an alarm device, adaptedto be connected toa source of gas of an anesthetic machine, having a chamber arranged to receive gas from said source, and a flexible diaphragm member forming a Wall thereof, movable in response to predetermined pressures within said chamber between two spaced operating positions, wherein the diaphragm is disposed in a first, or cocked operation position under nor but is restrained against movement out of cocked position until the pressure drops below the preselected pressure for actuating the alarm, whereupon the diaphragm is arranged to move substantially instantaneously to its second position. Signal actuating means, operatively connected to the diaphragm member, are energized and actuate signal means to give an alarm signal only when the plate member moves to its second position. In a preferred embodiment of the invention the diaphragm member comprises a flexible, metallic, snap-plate which is preshaped so as to extend inwardly of the chamber in the absence of external pressure acting thereon, but which flexes outwardly to its cocked, operating position when subjected to operating pressures. When the chamber pressure drops below the preselected alarm pressure the diaphragm plate snaps through its mid position and is displaced rapidly inwardly of the chamber to its second position thereby causing an acceleration of the signal actuating means and sufiiciently energizing it to actuate the signal means for the production of an intelligible alarm signal. The diaphragm is automatically reset to its cocked, operating position when normal operating pressures within the chamber are resumed.

Further objects and advantages of the invention may be better understood by reference to the following description of a preferred embodiment thereof and the accompanying drawings in which;

c Figure 1 is a vertical cross-sectional view of a bell alarm device embodying the features of the invention, illustrating the device under the influence of normal operating pressures;

. Figure 2- is a partial section of the apparatus shown in Figure 1, illustrating-the position thereof after the gas pressure has fallen below a predetermined value and a signal has been produced; and

Figure 3 is a partial side view looking from the right in Figure 1, illustrating the sliding interconnection of the diaphragm and pivoted striking arm of the bell.

Referring now to the drawing, the numeral designates the wall of a cabinet forming a part of a conventional anesthetic machine for administering inhalant anesthetics to patients. Such gas machines are well known to those skilled in the art and need not be described herein. A bell signal deviceindicated at 12, constructed in accordance with the present invention, is conveniently mounted Within said cabinet by means of a suitable supporting fixture 14 so that the structure will not interfere with the use and operation of the anesthetic machine but will be accessible if desired. The gases are metered by the operator using the usual control means provided in the conventional anesthetic gas machine and supplied to a breathing circuit for administration to the patient. A closed circuit arrangement for administering such anesthetic mixtures is illustrated in the Heidbrink, United States Patent No. 2,121,196. The manifold passage designated by the numeral 16 in Figure 1, corresponds to the manifold passage of an anesthetic machine through which one of the respective gases is fed from its source for delivery to the breathing circuit or inhaler. For the purpose of this description, the passage 16 may represent the passage connected with a gas source, such as a. cylinder of nitrous oxide gas.

The signal device 12 includes a cup-shaped body housing 18 which is mounted by means of retaining-screws 20 directly to the supporting fixture 14. A pressure responsive, plate diaphragm 22 preferably made of metal andrelatively thin in cross-section, is received in the open side of the body and seated therein against an O ring 24 which is seated in an annular recess 26. The diaphragm plate is'o'f substantially the same diameter as the opening 30 in which it is received and is pressed against the O-ring to form a peripheral gas-tight seal therewith by means of a retaining ring 28. The diaphragm member thus forms, in cooperation with the body 18, a gas chamber 32 which is connected by means of a tube 34 to the nitrous oxide conduit 16 so that this chamber is thereby subjected to substantially the same pressure as exists in the nitrousoxide conduit. The locking ring 28 is provided with anopening 36 through which the outer side of the diaphragm is exposed at all times to atmospheric pressure, such that the net gas pressure exerted thereon corresponds to the differential pressure between that in the chamber 32 and the atmospheric pressure.

A gong fi'l ismounted at the front of the housing 18 whereonit is secured by meansofa retaining screw 38. A clapper carried ona spring supporting arm 42 is disposed in alignment with the edge of the gong so that, upon actuation thereof as" hereinafter described, the gong 4 is struck by the clapper to produce a resonant, audible signal. The spring supporting arm 42 is anchored at its opposite end by means of one of the retaining screws 20, against the supporting fixture 14, which also serves to hold the body 18 in place.

The pressure diaphragm 22 carries substantially at its center an outwardly extending pin 46 which may be in the form of a screw as shown, the head of which is against the inner side of the diaphragm and the threaded stem of which extends therethrough. The head end of the screw is fixedly secured in a gastight manner to the diaphragm which may be, for example, by soldering. The pin 46 carries two nuts 48 which may be threaded to move lengthwise along the pin and which are arranged to grip between them a spacer 50. The projecting end of the stem 46 passes through an elongated slot 51 in the supporting arm 32, which is best seen in Figure 3. From this figure it will be seen that the nuts 48 are of larger diameter than'the width of the slot 51. The nuts are arranged to bear against opposite sides of the supporting arm and to thus adjust its angular position and cause it to pivot in response to movement of the diaphragm. The spacer 50 limits the approach of the nuts to one another in order to prevent them from tightening against the supporting arm which must be freely retained therebetween to accommodate its pivoting movement. This purpose is also served by the elongation of slot 51 within which relative translation of the spacer 50 is permitted during rotation of the supporting arm.

The clapper carried at the outer end of the supporting arm is displaced in accordance with the movement of the diaphragm and in proportion to the relative distances of the clapper and actuating stem from the point of pivoting of the supporting arm. The proper orientation of the supporting arm with respect to the gong is such that the clapper is slightly spaced therefrom when the diaphragm is in its innermost position. This position of the clapper is shown, for example, in Figure 2 and by the position indicated in dotted lines in Figure 1.

The outward deflection of the diaphragm is limited by its engagement with the radial, inwardly projecting portion 54 of the locking ring 28 which is adapted to back up the diaphragm when the chamber is subjected to normal operating pressures. Such additional support serves to prevent permanent deformation of the diaphragm plate in the event that the chamber is subjected to pressures above those for which it is ordinarily intended.

The clapper is caused to strike the bell and thus produce a signal by accelerating the clapper toward the gong. When the clapper has moved inwardly to the position corresponding to that shown in the dotted lines, the acceleration imparted to it produces sufficient momentum that the spring supporting arm 42 bends, permitting the clapper to travel the additional distance required for it to strike the edge of the gong. Following the impact, the clapper is retracted by the spring arm and comes to rest at the position spaced from the gong as shown in Figure 2.

The energization of the clapper arm, suificient to strike the gong, is imparted by movement of the diaphragm plate 22 which undergoes a rapid snapping action from its cocked position to its inner position when the chamber pressure drops below a predetermined value. This operation is achieved by the fact that the diaphragm 22 is preformed so as to have a slight inward bulge, exclusive of outside forces acting thereon, corresponding to the position thereof as shown in Figure 2. The diaphragm, in the form of a disk, is sufiiciently thin and flexible that it can bend outwardly to the position shown in Figure 1 when the chamber 32 is subjected to normal operating pressures. In doing so, the central portion of the diaphragm must be forced through a so-called intermediate, or'mid, position which is substantially in the plane of its outer peripheral rim. Due to such construction of the diaphragm plate and the fact that it is confined around its periphery between the locking ring and the body housing, it will be seen that it possesses a tendency to snap with extreme rapidity in either direction once displaced'slig'htly on either side of such mid position. Thus, as the chamber pressure progressively diminishes during use of the gas, from the normal range of operating pressures to slightly above a preselected alarm pressure, the diaphragm may be retracted substantially to an intermediate position but remains cockedf and does not pass through such position. It will be seen'that the'so called normal operating'or cocked position of=the diaphragm. may be viewed as any position on the outside of its mid position in which the diaphragm is constrained against movement to its inner position by gas pressures above the preselected alarm pressure. As soon as the pressure in the chamber is reduced belowsuch preselected alarm pressure, the return or spring back tendency of the diaphragm is sulficient to move it through the mid position and the diaphragm then snaps rapidly back to its initial shape. The rapid motion thereof, transmitted through the connecting post 46, aifords the necessary acceleration to propel the clapper into engagement with the gong. On the other hand, as mentioned above, when the diaphragm is once again at rest the clapper will be out of engagement with the gong which, as will be readily understood, permits full resonance of the gong to be obtained.

It will be seen that the shape of the diaphragm provides resistance to outward deflection and produces an internal stress when it is deflected to its outer position under gas pressure, which tends to return the diaphragm inwardly. Such resistance to outward deflection and return tendency depend upon the configuration of the diaphragm including, for example, the efiective area, thickness and the extent of the residual inward deformation. As will be well understood by those skilled in the art, these may be selected such that the diaphragm will respond to preselected gas pressures.

It will be seen, of course, that the spring arm 42 also may contribute some inwardly acting force on the diaphragm which may alfect the pressure at which the diaphragm will snap back. Similarly, other external means, such as a separate spring member, might be employed to cooperate with the diaphragm to furnish an additional inward force thereagainst. In instances such as this, the means furnishing such additional return force might be employed to vary the responding gas pressure for motivating the diaphragm. It is preferred, however, that the influence of the spring arm 42 be made substantially negligible, so that inward or outward adjustment thereof by threading of the positioning nuts along the diaphragm stem 46, when positioning the clapper element with respect to the gong, will have substantially no influence upon the pressure at which the alarm will be energized.

As an illustration of the adaptation of the alarm device hereinabove described to a source of nitrous oxide for anesthetic administration, the plate diaphragm advantageously may be arranged to flex outwardly to its cocked position in response to a chamber pressure of about 26 p.s.i. The usual operating pressures for nitrous oxide which exist in the delivery conduit 16 shown in Figure 1 generally may be in the range of from 37 to 50 p.s.i. These pressures correspond to the pressure delivered by a regulator from which the nitrous oxide gas is dispensed from a source such as a compressed gas cylinder. Such conduit pressures, of course, are further reduced to administration pressures of slightly above atmospheric pressures by further valve means before the gas is introduced into the breathing device or circuit. The diaphragm may be arranged to snap back to its initial position when the chamber pressure drops to about 6 p.s.i. It will be understood that such a drop of pressure in the conduit 16 will occur as the cylinder approaches exhaustion, or in the event of an interruption in the delivery of gas. Upon actuation of the alarm in response to such drop in pressure, the operator will be immediately appraised of this fact and may make any necessary adjustments or supply the gas from a'separate or fresh cylinder and thereby avoid hazard to the patient- It should be understood that the signal device is not intended to.substitute for, or take the place of, the conventional means upon which the anesthetist relies in present administration apparatus for determining the adequacy of the available gas supply. Thus, the pressure gage associated with the gas source and the flow metering tube through which the gas is delivered are still used and constitute a first line of assurance of proper operation of the apparatus. However, the signal device described herein, by its attachment to such anesthetic apparatus, affords an additional safeguard which serves to give warning to the anesthetist in the event that due to oversight or other mishap, the supply of gas has been depleted or interrupted without his awareness thereof.

In one specific embodiment of the alarm device for operation as described above, a diaphragm plate corresponding to the diaphragm 22 was employed which was in the form of a disc made of Phosphor bronze having an overall diameter of 2%; inches; an effective area of 2% square inches enclosed by the O-ring seal; and, a crosssectional thickness of .020 inch. The disc was deformed by impressing therein a substantially conical bulge whose maximum deformation from the plane of the fiat disc was approximately .050 inch.

It will be understood that the apparatus herein described and illustrated in the accompanying drawing is a preferred embodiment of the invention and that various modifications and changes may be made without departing from the spirit of the invention as defined by the following claims.

I claim:

1. A signal device responsive to a change in the differential pressure between a reference pressure and a range of operating pressures comprising a chamber adapted to be subjected to said operating pressures, a flexible diaphragm plate, forming a wall of said chamber subjected on the outer side thereof to said reference pressure, said diaphragm plate being initially distorted such that its central portion bulges out of the plane of the peripheral portion thereof corresponding to a first position of said diaphragm and having a second position corresponding to the position of the diaphragm when flexed to the opposite side of the plane of its peripheral portion under the influence of pressure acting thereon, and a mid position substantially in the plane of the periphery of said diaphragm, said diaphragm being unstable in its mid position and tending to snap rapidly in either direction when displaced slightly on either side of said mid position, actuating means operatively connected with said diaphragm activated by the rapid movement of said diaphragm through said mid position in response to the application of a predetermined pressure differential thereon and signal producing means energized by said actuating means.

2. A signal device according to claim 1 wherein said signal producing means is a percussion member and said actuating means includes resilient means, said actuating means being normally spaced from said percussion member throughout the limits of displacement of said diaphragm and being energized by acceleration in response to movement of said diaphragm sufliciently to be defiected beyond its normal limits to strike said signal producing means.

3. An alarm device responsive to a change in gas pressure from a normal range of operating pressures to a pressure below a predetermined pressure comprising a gong, a clapper normally spaced from said gong, supported on a resilient striker arm, a gas chamber adapted to be subjected to a source of gas under pressure, an inwardly deformed, flexible, metal diaphragm plate forming a wall of said chamber and means operatively connecting said diaphragm plate and said supporting arm,

said plate being movable to an outer position tinder nor mal operating pressures subject to a stress produced by such movement tending to return said diaphragm to its inner position and being characterized by a tendency to remain in said outer position as long as said chamber pressure exceeds a preselected pressure and to move substantially instantaneously to said inner position when the gas pressure drops below said preselected pressure.

4. An alarm device according to claim 3 wherein said striker arm is a pivoted element arranged to rotate in'the direction of movement of said diaphragm plate, said means operatively connecting said diaphragm plate and said striker arm include a pin member extending outwardly from said diaphragm and having a linkage connection including means on said pin engageable with op- 15 bosite Sides of a str k r. weav new pression of the striker arm therebetween, to move said 8 striker arm in response to movement of said diaphragm and affording relative translational movement of said striker arm respect; to s iidpi'nto accommodate the arcuate movementof 'said'a'fin. i

5. An alarm device accoiaifi to claim 4 wherein said linkage connection is longitudinallyadjustable on said p n member to permit adjustment of the'spacirig' of said clapper With respect to said gong.

References Cited in the file of this patent UNITED STATES PATENTS 493,265 Hasey Mar. 14, 1893 FOREIQN PATENTS 28,147 G'reatBritain of 1897 26,624 Aas triau'nun Dec. 10, 1906 

